Comparing mixed media and conventional slow sand filters for arsenic - - PowerPoint PPT Presentation

▶

Jan 16, 2024 98 likes •218 views

Comparing mixed media and conventional slow sand filters for arsenic removal from groundwater K.M. miech , A. Tolsma, T. Kovcs , R. Bekius, V. Dalbosco, K. Yasadi, L.Groendijk , L.L.F. Agostinho Athens, September 2016 1 Outlook

SLIDE 1

Comparing mixed media and conventional slow sand filters for arsenic removal from groundwater

K.M. Śmiech, A. Tolsma, T. Kovács, R. Bekius, V. Dalbosco, K. Yasadi, L.Groendijk, L.L.F. Agostinho Athens, September 2016 1

SLIDE 2

Outlook

Background: arsenic contamination of groundwater in Bangladesh
Methods
Setup design
Results
As removal efficiency
Vertical As concentration profiles
Raman analysis of F2 media
Conclusions

SLIDE 3

Arsenic contamination of groundwater in Bangladesh

Arsenic in drinking water via hand tube wells
Chakraborti et al. (2010):
36 million people  As > 10 µg L-1 (WHO guideline)
22 million people  As > 50 µg L-1 (Bangladesh government)
Health risks:
Skin lesions
Lung irritation
Cancer (skin, bladder...)
Solution:
SSF augmented with iron

Chakraborti et al. (2010) Status of groundwater arsenic contamination in Bangladesh. A 14-year study report. Water Research 2010, 44 (19), 5789-5802

SLIDE 4

Methods

Three filters:
F1: Conventional (reference)
F2: Corrosive iron matter (CIM)
F3: Iron coated sand
Filtration rate: 6 L h-1
Continuous operation for 260 days
Inlet As concentration: 70 μg L-1
Constant temp. 26°C
Online measurements:
pH
Redox potential
Electrical conductivity
Total As analysis in inlet and outlet twice per day
Total As samples along the filter column
Raman analysis of solid filter media

SLIDE 5

Setup design

SLIDE 6

As removal efficiency

SLIDE 7

Vertical As concentration profiles

SLIDE 8

Raman analysis of F2 media

Raman spectroscopy:

80% lepidocrocrite (ɣ-FeOOH)
20% hydrous ferric oxides
traces geothite (α-FeOOH)
no magnetite

Mass balance DO and Fe:

80% CIM oxidized

F3: lower As removal efficiency due to PO4

3-, CO3 2- occupying surface sites 8

SLIDE 9

Conclusions

SSF augmented with CIM could efficiently

remove As below the 10 µg L-1 WHO guideline for a prolonged time of continuous operation (200 days, 6 L d-1)

As removal occurred inside CIM layer
80% CIM oxidized to lepidocrocite and HFO
Active sites in iron coated sand occupied by

PO4

3- and CO3 2- during retreatment, preventing

efficient As removal

SLIDE 10

Acknowledgements

SLIDE 11

Thank you very much!

Questions?

karolina.smiech@hvhl.nl